/// <summary>
/// If any expression nodes cache any state for the duration of evaluation,
/// now's the time to clean it up
/// </summary>
internal override void ResetState()
{
if (_leftChild != null)
{
_leftChild.ResetState();
}
if (_rightChild != null)
{
_rightChild.ResetState();
}
}
/// <summary>
/// Evaluates a string representing a condition from a "condition" attribute.
/// If the condition is a malformed string, it throws an InvalidProjectFileException.
/// This method uses cached expression trees to avoid generating them from scratch every time it's called.
/// This method is thread safe and is called from engine and task execution module threads
/// Logging service may be null.
/// </summary>
internal static bool EvaluateConditionCollectingConditionedProperties <P, I>
(
string condition,
ParserOptions options,
Expander <P, I> expander,
ExpanderOptions expanderOptions,
Dictionary <string, List <string> > conditionedPropertiesTable,
string evaluationDirectory,
ElementLocation elementLocation,
ILoggingService loggingServices,
BuildEventContext buildEventContext,
ProjectRootElementCache projectRootElementCache = null
)
where P : class, IProperty
where I : class, IItem
{
ErrorUtilities.VerifyThrowArgumentNull(condition, "condition");
ErrorUtilities.VerifyThrowArgumentNull(expander, "expander");
ErrorUtilities.VerifyThrowArgumentLength(evaluationDirectory, "evaluationDirectory");
ErrorUtilities.VerifyThrowArgumentNull(buildEventContext, "buildEventContext");
// An empty condition is equivalent to a "true" condition.
if (condition.Length == 0)
{
return(true);
}
// If the condition wasn't empty, there must be a location for it
ErrorUtilities.VerifyThrowArgumentNull(elementLocation, "elementLocation");
Hashtable cachedExpressionTreesForCurrentOptions = s_cachedExpressionTrees[(int)options];
// We only need to lock on writes to the table
if (cachedExpressionTreesForCurrentOptions == null)
{
// Given property functions, casing in conditional expressions isn't necessarily ignored.
cachedExpressionTreesForCurrentOptions = new Hashtable(50, StringComparer.Ordinal);
lock (s_cachedExpressionTrees)
{
s_cachedExpressionTrees[(int)options] = cachedExpressionTreesForCurrentOptions;
}
}
// VS stress tests could fill up this cache without end, for example if they use
// random configuration names - those appear in conditional expressions.
// So if we hit a limit that we should never hit in normal circumstances in VS,
// and rarely, periodically hit in normal circumstances in large tree builds,
// just clear out the cache. It can start repopulating again. Some kind of prioritized
// aging isn't worth it: although the hit rate of these caches is excellent (nearly 100%)
// the cost of reparsing expressions should the cache be cleared is not particularly large.
// Loading Australian Government in VS, there are 3 of these tables, two with about 50
// entries and one with about 650 entries. So 3000 seems large enough.
if (cachedExpressionTreesForCurrentOptions.Count > 3000) // threadsafe
{
lock (cachedExpressionTreesForCurrentOptions)
{
cachedExpressionTreesForCurrentOptions.Clear();
}
}
// Try and see if we have an expression tree for this condition already
GenericExpressionNode parsedExpression = (GenericExpressionNode)cachedExpressionTreesForCurrentOptions[condition];
if (parsedExpression == null)
{
Parser conditionParser = new Parser();
#region REMOVE_COMPAT_WARNING
conditionParser.LoggingServices = loggingServices;
conditionParser.LogBuildEventContext = buildEventContext;
#endregion
parsedExpression = conditionParser.Parse(condition, options, elementLocation);
// It's possible two threads will add a different tree to the same entry in the hashtable,
// but it should be rare and it's not a problem - the previous entry will be thrown away.
// We could ensure no dupes with double check locking but it's not really necessary here.
// Also, we don't want to lock on every read.
lock (cachedExpressionTreesForCurrentOptions)
{
if (!s_disableExpressionCaching)
{
cachedExpressionTreesForCurrentOptions[condition] = parsedExpression;
}
}
}
bool result;
ConditionEvaluationState <P, I> state = new ConditionEvaluationState <P, I>(condition, expander, expanderOptions, conditionedPropertiesTable, evaluationDirectory, elementLocation, projectRootElementCache);
// We are evaluating this expression now and it can cache some state for the duration,
// so we don't want multiple threads working on the same expression
lock (parsedExpression)
{
try
{
result = parsedExpression.Evaluate(state);
}
finally
{
parsedExpression.ResetState();
}
}
return(result);
}